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Filename : rfc4253.js
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// Copyright 2015 Joyent, Inc.

module.exports = {
	read: read.bind(undefined, false, undefined),
	readType: read.bind(undefined, false),
	write: write,
	/* semi-private api, used by sshpk-agent */
	readPartial: read.bind(undefined, true),

	/* shared with ssh format */
	readInternal: read,
	keyTypeToAlg: keyTypeToAlg,
	algToKeyType: algToKeyType
};

var assert = require('assert-plus');
var Buffer = require('safer-buffer').Buffer;
var algs = require('../algs');
var utils = require('../utils');
var Key = require('../key');
var PrivateKey = require('../private-key');
var SSHBuffer = require('../ssh-buffer');

function algToKeyType(alg) {
	assert.string(alg);
	if (alg === 'ssh-dss')
		return ('dsa');
	else if (alg === 'ssh-rsa')
		return ('rsa');
	else if (alg === 'ssh-ed25519')
		return ('ed25519');
	else if (alg === 'ssh-curve25519')
		return ('curve25519');
	else if (alg.match(/^ecdsa-sha2-/))
		return ('ecdsa');
	else
		throw (new Error('Unknown algorithm ' + alg));
}

function keyTypeToAlg(key) {
	assert.object(key);
	if (key.type === 'dsa')
		return ('ssh-dss');
	else if (key.type === 'rsa')
		return ('ssh-rsa');
	else if (key.type === 'ed25519')
		return ('ssh-ed25519');
	else if (key.type === 'curve25519')
		return ('ssh-curve25519');
	else if (key.type === 'ecdsa')
		return ('ecdsa-sha2-' + key.part.curve.data.toString());
	else
		throw (new Error('Unknown key type ' + key.type));
}

function read(partial, type, buf, options) {
	if (typeof (buf) === 'string')
		buf = Buffer.from(buf);
	assert.buffer(buf, 'buf');

	var key = {};

	var parts = key.parts = [];
	var sshbuf = new SSHBuffer({buffer: buf});

	var alg = sshbuf.readString();
	assert.ok(!sshbuf.atEnd(), 'key must have at least one part');

	key.type = algToKeyType(alg);

	var partCount = algs.info[key.type].parts.length;
	if (type && type === 'private')
		partCount = algs.privInfo[key.type].parts.length;

	while (!sshbuf.atEnd() && parts.length < partCount)
		parts.push(sshbuf.readPart());
	while (!partial && !sshbuf.atEnd())
		parts.push(sshbuf.readPart());

	assert.ok(parts.length >= 1,
	    'key must have at least one part');
	assert.ok(partial || sshbuf.atEnd(),
	    'leftover bytes at end of key');

	var Constructor = Key;
	var algInfo = algs.info[key.type];
	if (type === 'private' || algInfo.parts.length !== parts.length) {
		algInfo = algs.privInfo[key.type];
		Constructor = PrivateKey;
	}
	assert.strictEqual(algInfo.parts.length, parts.length);

	if (key.type === 'ecdsa') {
		var res = /^ecdsa-sha2-(.+)$/.exec(alg);
		assert.ok(res !== null);
		assert.strictEqual(res[1], parts[0].data.toString());
	}

	var normalized = true;
	for (var i = 0; i < algInfo.parts.length; ++i) {
		var p = parts[i];
		p.name = algInfo.parts[i];
		/*
		 * OpenSSH stores ed25519 "private" keys as seed + public key
		 * concat'd together (k followed by A). We want to keep them
		 * separate for other formats that don't do this.
		 */
		if (key.type === 'ed25519' && p.name === 'k')
			p.data = p.data.slice(0, 32);

		if (p.name !== 'curve' && algInfo.normalize !== false) {
			var nd;
			if (key.type === 'ed25519') {
				nd = utils.zeroPadToLength(p.data, 32);
			} else {
				nd = utils.mpNormalize(p.data);
			}
			if (nd.toString('binary') !==
			    p.data.toString('binary')) {
				p.data = nd;
				normalized = false;
			}
		}
	}

	if (normalized)
		key._rfc4253Cache = sshbuf.toBuffer();

	if (partial && typeof (partial) === 'object') {
		partial.remainder = sshbuf.remainder();
		partial.consumed = sshbuf._offset;
	}

	return (new Constructor(key));
}

function write(key, options) {
	assert.object(key);

	var alg = keyTypeToAlg(key);
	var i;

	var algInfo = algs.info[key.type];
	if (PrivateKey.isPrivateKey(key))
		algInfo = algs.privInfo[key.type];
	var parts = algInfo.parts;

	var buf = new SSHBuffer({});

	buf.writeString(alg);

	for (i = 0; i < parts.length; ++i) {
		var data = key.part[parts[i]].data;
		if (algInfo.normalize !== false) {
			if (key.type === 'ed25519')
				data = utils.zeroPadToLength(data, 32);
			else
				data = utils.mpNormalize(data);
		}
		if (key.type === 'ed25519' && parts[i] === 'k')
			data = Buffer.concat([data, key.part.A.data]);
		buf.writeBuffer(data);
	}

	return (buf.toBuffer());
}